Power detectors sample RF signals, and generate an output voltage corresponding to the power of the sampled signal. Depending on the type of power detector, the output voltage is proportional to either the root mean squared (rms) value, the log value, or a peak value of the sampled signal.
Transmitters may use power detectors to monitor and control transmitted signal power levels. For example, a power detector may quantify the signal power output by the transmitting antenna. If the output signal power is too high, the gain of a power amplifier that feeds signals to the transmitting antenna may be decreased. If the output signal is too low, the gain may be increased. These gain adjustments may be incorporated in feedback loops.
Receivers may use power detectors to monitor received signal power levels. For example, a power detector may quantify the received signal level at the receiving antenna. If the received signal power is too high, the gain of a low noise amplifier, which amplifies the received signal from the receiving amplifier, may be decreased. If the received signal power is too low, the gain may be increased. As with transmitters, these gain adjustments may be incorporated in feedback loops.